Analysis and investigation of the leakage failure of a casing used in a shale gas well

•Reported a rare casing leakage failure in a shale gas well in western China during pressure testing.•Failure analysis of the casing and investigation of the manufacturing plant revealed that during the steel pipe rolling process, the bolts on the balance cylinder of the continuous pipe mill dropped onto the pipe. The bolt acts as a dissimilar metal substance to destroy the continuity of the metal.•The FEA calculation results show that when the casing is used in the field, under axial tension and internal pressure, the equivalent force at the defect is much greater than the yield strength of the casing. Therefore, the crack at the defect quickly propagated and penetrated the entire wall thickness of the casing, resulting in the final failure of the casing.•In order to avoid the recurrence of such failure accidents, rectification suggestions were put forward.